Serve them open so everyone can add their own sauce. Try 50/50 beef and pork mince and add a teaspoon of paprika to the meat — it adds depth. Wet your hands before shaping the patties or the meat sticks to everything.
The food processor does two jobs here — blitzing the onion into the meat gives a much better texture than hand mixing. Wet your hands before shaping the patties or the meat sticks to everything. Serve them open so everyone can build their own — ketchup, mustard, hot sauce, whatever they want on top.
Use GF brioche-style buns — widely available in supermarkets. Everything else is naturally gluten free.